All you need to know about physics in games

The more physics, the greater the potential

The most exciting development for in-game physics in the last couple of years hasn't been cards, but rather Euphoria – a behaviour based engine aimed at in-game characters. It's not geared towards physics in itself, certainly not in the same way as Havok and PhysX, but it definitely contributes to the overall effect within a proper world simulation.

One of the first uses of dedicated physics coding in games was for 'ragdoll' effects – in short, making enemies react properly after death. By giving each character model a full skeleton, connected and animated using inverse kinematics, the limp corpse could half- hang over railings, slip down stairs, or even be picked up and rearranged into hilarious screenshots to amuse the whole internet. Well, in theory…

This was one of the most visible demonstrations of in-game physics until Half-Life 2 came along, and notable because it only kicked in after death – actual actions were still a matter for key-framed animation, unstoppable, unchangeable, and often clunky.

Euphoric behaviour

Euphoria changes this by focusing not on individual animations but 'behaviours', with characters given instructions of how to act, and the freedom to do so within the physical simulation. Where a regular character might be stuck watching the player escape on a moving platform, a Euphoria powered one might leap across, grab the edge with one hand, and clamber up to continue the fight.

Instead of each hit part of the body counting, a player could shoot a character in the leg and watch it react with a pain animation before falling flat on its backside with a scream. As with ragdolls and other physics engines, none of this happens magically – the developers still have to make it all work, and tell the characters how to react. But it opens the door for far more realistic situations, and most importantly, more unique gaming experiences than any canned animation could attempt to provide.

Grand Theft Auto 4 was the first game to ship with Euphoria support with one of the most amusing examples. Victims of carjacking are now likely to wind up taking a long trip after trying to take back their property when you've already got your foot on the pedal. with one hand on the handle, they will bounce up and down on the road until shaken loose.

Other games due to ship with Euphoria support include Lucasarts' Sith-simulator The Force Unleashed, the next Indiana Jones game, and an American football title, Backbreaker.

The Future of Physics

Right now, adding an impressive physics engine is seen as a selling point in itself, but as with the advances in 3D graphics, this won't last for long. However, when you've played in a world that makes you feel like you're there, nothing else will ever feel quite right again.

Just step back a few years to games without skeletal animation systems, or the completely canned deaths that were vogue before ragdolls, and you'll see just how important even the smallest details are. The goal for makers of physics engines isn't anything as specific as photorealism or the creation of a sentient computer, but for a game's world that is consistent, accessible and without barriers to the player.

The irony is that when developers finally succeed, the results are going to be so good, you'll be too busy enjoying it to notice.